A Comparison of Regional Blood Flow and Oxygen Utilization During Dynamic Forearm Exercise in Normal Subjects and Patients with Congestive Heart Failure

Abstract

SUMMARYPatients with severe congestive heart failure (CHF) have been found to have a diminished response to the metabolic arteriolar dilator stimulus of ischemia. In order to evaluate a more physiologic stimulus and the possible metabolic consequences of this vascular abnormality, 22 normal subjects (N) and seven patients with severe CHF performed rhythmic forearm exercise by squeezing a rubber bulb to 25, 50, or 100 mm Hg for 5 sec, four times/min, for 5 min. During the last half of the 10 sec relaxation phases, forearm blood flow (FBF) was measured plethysmographically. Not only was FBF reduced at rest in CHF (CHF: 2.00 i 0.31; N: 3.10 ± 0.27 ml/min 100 ml, P < 0.02) but it was reduced at each level of exercise as well (CHF: 4.05 0.71, 5.57 + 0.71, 6.68 + 3.09; N: 7.10 ± 0.76, 11.15 ± 1.24, 20.32 ± 1.93 ml/min. 100 ml, P < 0.01). Forearm oxygen extraction, calculated from brachial venous and systemic arterial blood, was consistently increased in CHF and was sufficient to maintain a normal forearm oxygen consumption at rest (CHF: 0.14 ± 0.04; N: 0.12 + 0.01 ml 02/min 100 ml, P < 0.5). During exercise the calculated index of oxygen consumption was reduced at all levels of exercise (CHF: 0.30 0.04, 0.48 + 0.09, 0.54 + 0.14; N: 0.51 ± 0.05, 0.89 i 0.08, 1.63 + 0.13 ml 02/min 100 ml, P < 0.01). These differences persisted despite alpha-adrenergic blockade with phentolamine and suppression of skin flow in N by epinephrine iontophoresis. Therefore, at comparable levels of dynamic forearm exercise patients with CHF DURING DYNAMIC EXERCISE patients with congestive heart failure (CHF) appear to have an exaggerated sympathoadrenal response which results in a decreased perfusion of regional circulations that have low metabolic requirements and adequate alpha-adrenergic receptor sites.'`6 A similar increase in alpha-adrenergic tone also occurs in exercising skeletal muscle. However, these constrictor impulses are offset by the local accumulation of metabolites and a vasodilation occurs.7' 8 Therefore, in exercising muscle, vascular resistance falls and oxygen delivery increases. It is important to note that patients with CHF demonstrate a reduced metabolic arteriolar dilator response following restoration of flow to an ischemic limb (reactive hyperemia) which is considerably reduced when compared with that of normal subjects.9 This relative arteriolar stiffness has been postulated to be a possible protective mechanism for

Short-Term Physical Training Improves Vasodilatory Capacity in Cardiac Patients.

“…Effects of physical training on cardiovascular function: Inappropriate distribution of blood flow to exercising muscles has been implicated as an important mechanism of exercise limitation in cardiac patients. 2,[24][25][26][27][28][29][30][31][32] Decreased muscular power as well as metabolic and endocrine disorders are also known as factors of exercise limitation. 9,[33][34][35][36][37] In 1968, Zelis, et al reported a decreased vasodilatory capacity in cardiac patients.…”

In Vivo and In Vitro Evidence for Impaired Arginine Transport in Human Heart Failure

“…[1][2][3][4][5][6] Furthermore, these observations have been confirmed by use of a more physiological stimulus such as exercise and the hyperemia induced by ischemia. 7,8 Although the evidence for reduced endothelial function in congestive heart failure (CHF) is compelling, the mechanisms responsible for this phenomenon remain unclear. In broad terms, potential mechanisms include reduced expression of muscarinic cholinergic receptors on endothelial cells, altered intracellular signaling, reduced nitric oxide (NO) production, increased NO degradation, or an attenuated response by the intracellular targets of NO or cGMP.…”

Exercício resistido na avaliação da disfunção endotelial na insuficiência cardíaca

“…Each individual was asked to perform three maximum handgrip movements. The value considered as maximum handgrip strength was the arithmetical mean of the strength obtained at the three gripping movements performed with the pneumatic bag 21 . This value was used for the calculation of the exercise load to be applied.…”

“…After a 30-minute rest, brachial artery diameter and flow velocity parameters were reassessed under a new basal condition (B2 condition). After that, each subject received the same pneumatic bag which was utilized to assess maximum handgrip strength capacity and they were asked to performed repeated gripping and relaxation movements with the left hand, with 75% of the maximum load (EX75 condition), in a protocol adaptation developed for this purpose 21 . After the fi rst minute of exercise, the aforementioned parameters in brachial territory were assessed.…”